You can't scale up the Magic Kingdom, no. But Disney had a pattern going for a while where they opened a new Florida park every 10 years or so: 1971, 1982, 1989, 1998. That probably helped a lot. They've done some small expansions in the existing parks since then, but they're about 20 years behind in adding a new park. I think that's a huge part of the crowding issue now.

(Now Anaheim, there they're kind of hosed. No space to expand.)